A connection can be established via the connection builder functions.
The org_example_ping::VarlinkClient implements org_example_ping::VarlinkClientInterface,
which has all the varlink methods (names converted from camel case to lowercase snake case).
The PingString() method would be named ping_string().

To iterate over a more call

for reply in my_more_service.test_more(/* params */).more()?{/*...*/}

The reply struct is placed in a structure named after the method with _Reply appended.
So, the reply to the Ping() method in our example is in a struct called Ping_Reply.